U.S. patent number 8,980,649 [Application Number 14/028,216] was granted by the patent office on 2015-03-17 for method for manufacturing non-volatile magnetic memory cell in two facilities.
This patent grant is currently assigned to Avalanche Technology, Inc.. The grantee listed for this patent is Avalanche Technology, Inc.. Invention is credited to Parviz Keshtbod, Roger Klas Malmhall, Rajiv Yadav Ranjan.
United States Patent |
8,980,649 |
Ranjan , et al. |
March 17, 2015 |
Method for manufacturing non-volatile magnetic memory cell in two
facilities
Abstract
In accordance with a method of the present invention, a method
of manufacturing a magnetic random access memory (MRAM) cell and a
corresponding structure thereof are disclosed to include a
multi-stage manufacturing process. The multi-stage manufacturing
process includes performing a front end on-line (FEOL) stage to
manufacture logic and non-magnetic portions of the memory cell by
forming an intermediate interlayer dielectric (ILD) layer, forming
intermediate metal pillars embedded in the intermediate ILD layer,
depositing a conductive metal cap on top of the intermediate ILD
layer and the metal pillars, performing magnetic fabrication stage
to make a magnetic material portion of the memory cell being
manufactured, and performing back end on-line (BEOL) stage to make
metal and contacts of the memory cell being manufactured.
Inventors: |
Ranjan; Rajiv Yadav (San Jose,
CA), Keshtbod; Parviz (Los Altos Hills, CA), Malmhall;
Roger Klas (San Jose, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Avalanche Technology, Inc. |
Fremont |
CA |
US |
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Assignee: |
Avalanche Technology, Inc.
(Fremont, CA)
|
Family
ID: |
41016399 |
Appl.
No.: |
14/028,216 |
Filed: |
September 16, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140017818 A1 |
Jan 16, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12040827 |
Feb 29, 2008 |
8535952 |
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11674124 |
Feb 12, 2007 |
8084835 |
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14028216 |
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11678515 |
Feb 23, 2007 |
8058696 |
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14028216 |
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11739648 |
Apr 24, 2007 |
8183652 |
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11776692 |
Jul 12, 2007 |
8063459 |
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11860467 |
Sep 24, 2007 |
8018011 |
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11866830 |
Oct 3, 2007 |
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60853115 |
Oct 20, 2006 |
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60777012 |
Feb 25, 2006 |
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Current U.S.
Class: |
438/3;
257/E21.665; 257/E27.005 |
Current CPC
Class: |
B82Y
10/00 (20130101); G11C 11/16 (20130101); B82Y
25/00 (20130101); H01L 43/12 (20130101); H01L
27/228 (20130101) |
Current International
Class: |
H01L
21/00 (20060101) |
Field of
Search: |
;438/3
;257/E21.665,E27.005 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Huynh; Andy
Attorney, Agent or Firm: Imam; Maryam IPxLaw Group LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 12/040,827, filed on Feb. 29, 2008, by Rajiv Yadav Ranjan, and
entitled "Method For Manufacturing Non-Volatile Magnetic Memory",
which is a continuation-in-part of U.S. application Ser. No.
11/674,124 filed on Feb. 12, 2007, entitled "Non-Uniform Switching
Based Non-Volatile Magnetic Based Memory," which claims priority to
U.S. Provisional Application No. 60/853,115 filed on Oct. 20, 2006
entitled "Non-Uniform Switching Based Non-Volatile Magnetic Based
Memory"; and is a further continuation-in-part of U.S. application
Ser. No. 11/678,515 filed Feb. 23, 2007, entitled "A High Capacity
Low Cost Multi-State Magnetic Memory," which claims priority to
U.S. Provisional Application No. 60/777,012 filed Feb. 25, 2006
entitled "A High Capacity Low Cost Multi-State Magnetic Memory";
and is a further continuation-in-part of U.S. application Ser. No.
11/739,648, filed Apr. 24, 2007 entitled "Non-Volatile Magnetic
Memory with Low Switching Current and High Thermal Stability"; and
is a further continuation-in-part of U.S. application Ser. No.
11/776,692, filed Jul. 12, 2007, titled "Non-Volatile Magnetic
Memory Element with Graded Layer"; and is a further
continuation-in-part of U.S. application Ser. No. 11/860,467 filed
Sep. 24, 2007, titled "Low cost multi-state magnetic memory"; and
is a further continuation-in-part of U.S. application Ser. No.
11/866,830 filed Oct. 3, 2007 entitled "Improved High Capacity Low
Cost Multi-State Magnetic Memory"; and is a further
continuation-in-part of U.S. Application No. Not Yet Assigned filed
concurrently herewith entitled "An Improved Low Resistance High-TMR
Magnetic Tunnel Junction and Process for Fabrication Thereof."
Claims
What is claimed is:
1. A method of manufacturing a magnetic random access memory (MRAM)
cell comprising performing a front end on-line (FEOL) stage, in a
first facility, to make logic and non-magnetic portions of a memory
cell being manufactured including the steps of, forming an
intermediate interlayer dielectric (ILD) layer in the first
facility; forming intermediate metal pillars embedded in the
intermediate ILD layer in the first facility; and depositing a
conductive metal cap on top of the intermediate ILD layer and the
metal pillars to seal the intermediate ILD layer and the
intermediate metal pillars, wherein after the depositing step, a
FEOL stage structure is formed; performing magnetic fabrication
stage, in a second facility separate and apart from the first
facility, to make a magnetic material portion of the memory cell
being manufactured; and performing back end on-line (BEOL) stage,
in the second facility to make metal and contacts of the memory
cell being manufactured.
2. A method of manufacturing, as recited in claim 1, wherein the
FEOL stage further includes the steps of: forming logic on top of a
wafer, onto which memory cells are to be formed; forming a first
ILD layer on top of the logic; and forming a plurality of first
metal pillars dispersed in the first ILD layer.
3. A method of constructing a MRAM memory cell, as recited in claim
2, where the first metal pillars are made of tungsten.
4. A method of constructing a MRAM memory cell, as recited in claim
2, where the intermediate ILD layer is formed using a damascene
process comprising: forming a intermediate ILD layer on top of the
first ILD layer and first metal pillars; depositing photo resist on
top of the intermediate ILD layer in a manner which covers
substantially all of the ILD layer except the portion above the
first metal pillars; etching the intermediate ILD layer until the
first metal pillars are exposed; depositing a metal layer until the
metal contacts the exposed, first metal pillars; planerizing the
metal leaving in place the second metal pillars.
5. A method of constructing a MRAM memory cell, as recited in claim
4, where the second metal pillars are formed from copper.
6. A method of constructing a MRAM memory cell, as recited in claim
1, where the intermediate ILD layer etching is done using reactive
ion etching (RIE).
7. A method of constructing a MRAM memory cell, as recited in claim
2, where the intermediate ILD layer is formed using a non-damascene
process comprising: depositing a metal layer on top of the first
ILD layer and first metal pillars; depositing photo-resist pillars
on top of the metal layer in a pattern substantially above the
first metal pillars; etching the metal layer until the second metal
pillars remain; depositing an ILD layer covering the entire wafer
including the second metal pillars; planerizing the ILD layer until
the tops of the second metal pillars are exposed.
8. A method of constructing a MRAM memory cell, as recited in claim
2, where the second metal pillars are formed of copper.
9. A method of constructing a MRAM memory cell, as recited in claim
2, where the metal layer etching is done using reactive ion etching
(RIE).
10. A method of constructing a MRAM memory cell, as recited in
claim 2, where the first conductive metal cap is made of Tantalum,
Tantalum Nitride, Titanium, Titanium Nitride, Chromium, Tungsten,
Niobium or alloys containing one or more of these elements.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetic memory and
particularly to methods of manufacturing magnetic memory.
2. Description of the Prior Art
Computers conventionally use rotating magnetic media, such as hard
disk drives (HDDs), for data storage. Though widely used and
commonly accepted, such media suffer from a variety of
deficiencies, such as access latency, higher power dissipation,
large physical size and inability to withstand any physical shock.
Thus, there is a need for a new type of storage device devoid of
such drawbacks.
Other dominant storage devices are dynamic random access memory
(DRAM) and static RAM (SRAM) which are volatile and very costly but
have fast random read/write access time. Solid state storage, such
as solid-state-nonvolatile-memory (SSNVM) devices having memory
structures made of NOR/NAND-based Flash memory, providing fast
access time, increased input/output (TOP) speed, decreased power
dissipation and physical size and increased reliability but at a
higher cost which tends to be generally multiple times higher than
hard disk drives (HDDs).
Although NAND-based flash memory is more costly than HDD's, it has
replaced magnetic hard drives in many applications such as digital
cameras, MP3-players, cell phones, and hand held multimedia devices
due, at least in part, to its characteristic of being able to
retain data even when power is disconnected. However, as memory
dimension requirements are dictating decreased sizes, scalability
is becoming an issue because the designs of NAND-based Flash memory
and DRAM memory are becoming difficult to scale with smaller
dimensions. For example, NAND-based flash memory has issues related
to capacitive coupling, few electrons/bit, poor error-rate
performance and reduced reliability due to decreased read-write
endurance. Read-write endurance refers to the number of reading,
writing and erase cycles before the memory starts to degrade in
performance due primarily to the high voltages required in the
program, erase cycles.
It is believed that NAND flash, especially multi-bit designs
thereof, would be extremely difficult to scale below 45 nanometers.
Likewise, DRAM has issues related to scaling of the trench
capacitors leading to very complex designs which are becoming
increasingly difficult to manufacture, leading to higher cost.
Currently, applications commonly employ combinations of EEPROM/NOR,
NAND, HDD, and DRAM as a part of the memory in a system design.
Design of different memory technology in a product adds to design
complexity, time to market and increased costs. For example, in
hand-held multi-media applications incorporating various memory
technologies, such as NAND Flash, DRAM and EEPROM/NOR flash memory,
complexity of design is increased as are manufacturing costs and
time to market. Another disadvantage is the increase in size of a
device that incorporates all of these types of memories
therein.
There has been an extensive effort in development of alternative
technologies such as Ovanic RAM (or phase-change memory),
Ferroelectric RAM (FeRAM), Magnetic RAM (MRAM), Nanochip, and
others to replace memories used in current designs such as DRAM,
SRAM, EEPROM/NOR flash, NAND flash and HDD in one form or another.
Although these various memory/storage technologies have created
many challenges, there have been advances made in this field in
recent years. MRAM seems to lead the way in terms of its progress
in the past few years to replace all types of memories in the
system as a universal memory solution.
One of the problems with prior art methods of producing MRAM is
that prior art methods are very costly. This high cost is driven by
the fact that prior art methods have a low memory-element-per-wafer
yield, are unreliable, and are not modular.
In MRAM production, as with many other type of memory production,
there is a fixed cost per-wafer. As a result, the more MRAM memory
cells that can be manufactured on a single wafer, the lower the
cost per memory cell. Prior art methods have an undesirably low
memory-element-per-wafer yield making each memory cell
correspondingly more costly.
A further problem with prior art methods is that the methods of
production are unreliable. Unreliable methods lead to the frequent
fabrication of non-functioning memory cells. Each non-functioning
unit increases the per-unit cost of the remaining, functioning
units.
Also, the non-modular nature of prior art methods exacerbates the
cost and reliability problems. The nature of complementary
metal-oxide-semiconductor (CMOS) production, used in many types of
RAM production, generally precludes the use of many materials
present in MRAM production inside CMOS facilities. Thus, with prior
art methods, a facility must be wholly converted to MRAM production
further increasing the costs. Additionally, contamination results
from an MRAM and CMOS combined processes.
These problems reduce MRAM's competitive edge relative to DRAM,
SRAM, EEPROM/NOR flash, NAND flash, and HDD storage solutions.
Thus, the need arises for a method of manufacturing a low cost
(high volume), high-yield, high-reliability magnetic memory.
SUMMARY OF THE INVENTION
Briefly, in accordance with a method of the present invention, a
method of manufacturing a magnetic random access memory (MRAM) cell
and a corresponding structure thereof are disclosed to include a
multi-stage manufacturing process. The multi-stage manufacturing
process includes performing a front end on-line (FEOL) stage to
manufacture logic and non-magnetic portions of the memory cell by
forming an intermediate interlayer dielectric (ILD) layer, forming
intermediate metal pillars embedded in the intermediate ILD layer,
depositing a conductive metal cap on top of the intermediate ILD
layer and the metal pillars, performing magnetic fabrication stage
to make a magnetic material portion of the memory cell being
manufactured, and performing back end on-line (BEOL) stage to make
metal and contacts of the memory cell being manufactured.
These and other objects and advantages of the present invention
will no doubt become apparent to those skilled in the art after
having read the following detailed description of the preferred
embodiments illustrated in the several figures of the drawing.
IN THE DRAWINGS
FIG. 1 shows a flow chart of the relevant steps performed for
manufacturing non-volatile magnetic memory cells (for example,
magnetic random access memory (MRAM)), in accordance with a method
of the present invention.
FIG. 2 presents a cross section of a memory cell 1, in accordance
with the techniques of FIG. 1.
FIG. 2a presents a cross section of a memory cell 1, in accordance
with the techniques of FIG. 1.
FIG. 2b shows the structure of the memory cell after the metal
deposition step 314 has been completed.
FIGS. 2c and 2d show the structure of the memory cell after the
metal area defining and etching step 315 has been completed.
FIG. 2e shows the structure of the memory cell after the ILD
deposition step 316 has been completed.
FIG. 2f shows the structure of the memory cell after the photo
resist deposition and etching step 317 has been completed.
FIG. 2g shows the structure of the memory cell after the metal
deposition step 318 has been completed.
FIG. 2h shows the structure of the memory cell after the ILD
planerization step 320 has been completed.
FIG. 2i shows a cross section of the wafer.
FIG. 2j shows the small hump 130 that forms above the MTJ 76 as
part of the deposition process.
FIG. 2k shows the ILD layer 118 is planerized using CMP until the
top of the passivation cap 80 is exposed.
FIG. 2l shows the CMP slurry is changed and the passivation cap 80
is planerized using CMP until the top of conductive metal pillar 78
is exposed.
FIGS. 3-23 show 3-dimensional views of the relevant part of a wafer
onto which memory cells are formed in accordance with the method of
FIG. 1.
FIG. 3 shows the structure of a number of memory cells after the
CMOS step 10 has been completed, the source, gate and drain are
shown to be formed substantially parallel to one another.
FIG. 3a shows the structure of the memory cell during step 12,
after photo resist has been applied to the top of the ILD layer
except in the contact definition area.
FIG. 3b shows the structure of the memory cell during step 12,
after the ILD layer has been etched and a metal material deposited
on top of the ILD layer.
FIG. 4 shows the structure of a number of memory cells after the
step 12. The memory cell is shown to include the drain, source, and
gate, ILD layer and metal contact pillar.
FIG. 5 shows the structure of a number of memory cells after step
14. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, and ILD layer.
FIG. 5a shows the structure of the memory cell during step 16 where
photo resist has been applied to the top of the ILD layer except
over the contact definition area.
FIG. 6 shows the structure of a number of memory cells after the
step 16. The memory cell is shown to include the drain, source, and
gate ILD layer, metal contact pillar, and a post-etch ILD layer
with pillar holes.
FIG. 7 shows the structure of a number of memory cells after the
step 18. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, post-etch ILD layer with
pillar holes, and metal material
FIG. 8 shows the structure of a number of memory cells after the
step 20. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, and metal
pillar.
FIG. 9 shows the structure of a number of memory cells after the
step 22. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar, and
conductive metal cap.
FIG. 10 shows the structure of six memory cells after the step 24.
The memory cell is shown to include the drain, source, and gate,
ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ film, and conductive metal cap/hard
mask.
FIG. 11 shows the structure of a number of memory cells after the
step 26. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ film, conductive metal cap/hard mask and
photo-resist pillars.
FIG. 12 shows the structure of six memory cells after the step 28.
The memory cell is shown to include drain, source, and gate, ILD
layer, metal contact pillar, ILD layer, metal pillar, conductive
metal cap, MTJ, and conductive metal cap/hard mask.
FIG. 13 shows the structure of a number of memory cells after the
step 30. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap/hard mask, and
passivation layer.
FIG. 14 shows the structure of a number of memory cells after the
step 32. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap/hard mask,
passivation layer, and photo resist pillars.
FIG. 15 shows the structure of a number of memory cells after the
step 34. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap/hard mask, and
passivation cap.
FIG. 16 shows the structure of a number of memory cells after the
step 36. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap/hard mask,
passivation cap, and ILD layer.
FIG. 17 shows the structure of a number of memory cells after the
step 38. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap layer, passivation
cap, ILD layer, and the metal layer.
FIG. 18 shows the structure of a number of memory cells after the
step 40. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap layer, passivation
cap, ILD layer, a metal layer, and a photo resist bars.
FIG. 19 shows the structure of a number of memory cells after the
step 42. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap layer, passivation
cap, ILD layer, and metal bars.
FIG. 20 shows the structure of a number of memory cells after the
step 44. The memory cell is shown to include the drain, source, and
gate, ILD layer, metal contact pillar, ILD layer, metal pillar,
conductive metal cap, MTJ, conductive metal cap layer, passivation
cap, ILD layer, metal bars, and a passivation layer.
FIG. 21 shows the structure of the memory cell 398 after step
314.
FIG. 22 shows the structure of the memory cell 398 after step
316.
FIG. 23 shows the structure of the memory cell 398 after steps 318
and 320.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Referring now to FIG. 1, a flow-chart of the relevant steps
performed for manufacturing non-volatile magnetic memory cells (for
example, magnetic random access memory (MRAM)) is shown in
accordance with a method of the present invention. In FIG. 1, a
damascene process is used to efficiently and reliably manufacture
arrays of memory cells, onto, for example, a wafer, which includes
many memory cells. In manufacturing MRAMs, a complimentary
metal-oxide-semiconductor (CMOS) as well as magnetic manufacturing
processes are employed. That is, magnetic memory is manufactured
using magnetic processes and logic or transistors, used to connect
the magnetic memory and other logic for addressing and/or reading
and writing to the magnetic memory, is manufactured generally using
CMOS processes. The method of FIG. 1 allows modularity of the CMOS
and magnetic processes in that the magnetic memory can be
manufactured at a processing plant (or facility) that is
independent and separate from a plant used to manufacture the
logic. Additionally, intermediate process control steps are
introduced to ensure that the process is within the process
tolerance limits for a high yielding low-cost manufacturing
process. Intermediate process control steps refer to wafer probing
step to ensure that the preceding process steps were completed
within specifications and are most efficiently inserted after step
20 in FIG. 1.
Multiple stages of manufacturing are employed for advantageously
causing modularity of manufacturing to reduce costs and
contamination. For example, during a front end on-line (FEOL) stage
15, logic and non-magnetic portions of a memory cell are
manufactured and during to a magnetic fabrication stage 25, the
magnetic material portion of the memory cell is manufactured.
Finally, a back end on-line (BEOL) stage 35 is employed to
manufacture metal and other types of contacts.
In FIG. 1, the FEOL stage 15 is shown to include steps 10-22, the
magnetic fabrication stage 25 is shown to include steps 24-34 and
the BEOL stage 35 is shown to include steps 36-46, in accordance
with a method of the present invention. Accordingly, the FEOL stage
15 is performed, followed by the magnetic fabrication stage 25,
followed by the BEOL stage 35.
Alternatively, the FEOL stage 15 includes steps 314-320 and 22 with
the steps 314-320 replacing the steps 14-20, respectively, in which
case steps 10 and 12 are performed followed by steps 314-320,
followed by the magnetic fabrication stage 25 followed by the BEOL
stage 35.
FIG. 2 presents a cross section of a memory cell 1, as the memory
cell is being built on top of a CMOS circuit element, which is
shown formed on a wafer 306, in accordance with the process of FIG.
1. More specifically, FIG. 2 shows a cross section of a single
non-volatile magnetic memory cell 1, in accordance with an
embodiment of the present invention. For ease of understanding,
FIGS. 1 and 2 are discussed interchangeably to further clarify
forming the memory cell 1.
Referring back to FIG. 1, a CMOS step 10 is performed, during which
logic (also known as semiconductor or circuit) is built. Such
semiconductor includes, for example, transistors. In the method of
FIG. 1, a transistor is fabricated and covered with a bottom
interlayer dielectric (ILD) layer, also known as pre-metal
dielectric, which is shown and discussed relative to FIG. 2 as an
ILD layer 67.
An exemplary structure formed at the completion of FIG. 1 is shown
in FIG. 2 where a transistor (or "circuit(s)", "semiconductor" or
"logic") 61 is formed on the wafer 306 above which is formed a
bottom ILD layer 67. The transistor 61 is shown in FIG. 2 to
include a source 60, drain 62, and a channel 64, and gate 69. The
gate 69 is electrically separated from channel with a thin gate
oxide. The gate oxide thickness is typically in the range from 2 nm
to 200 nm depending on the width of the gate (thickness .about.2%
of gate width). The ILD layer 67 serves as an insulating layer to
prevent the transistor 61 formed at step 10 from short circuiting
with circuitry that is not intended to be coupled to the transistor
(or undesirable electrical connections). The transistor 61 serves
as an access transistor for comparing the resistance of one or more
memory cells to a reference transistor for reading/writing from and
to the memory cell 1.
After the CMOS step 10, in FIG. 1, a contact definition step 12 is
performed. During the contact definition step 12, photo-resist 58
(shown in FIG. 3a) is applied to the entire top of the ILD layer 67
and a contact area 100 is defined. The contact area 100 is defined
as a portion on top of the ILD layer 67 that is situated above the
source 60, the gate 69 and the drain 62 of the transistor 61, as
shown in FIG. 2 and shown with further clarification in FIG. 3.
Photo-resist 58 is used to control an etching process by preventing
the material covered by the photo-resist from being etched. Thus,
the ILD layer 67 is prevented from being etched except above the
drain 62, the gate 69 and the source 60 where it is etched.
During the contact definition step 12 of FIG. 1, the ILD layer 67
of FIG. 2 is etched until the source 60, the gate 69 and drain 62
are exposed to form holes 302, 303 and 304. In an exemplary method,
reactive ion etching (RIE) is performed to expose the drain and
source of the transistor 61. It should be noted that the use of RIE
is exemplary only and that other etching methods are contemplated.
While other etching techniques are contemplated, an RIE process
having a substantially gaseous by-product is used in the method of
FIG. 1 to reduce the number of steps during manufacturing by
eliminating a clean-up step, which is discussed in further detail
below.
Thereafter, metal barrier (seed) layer 101 is deposited on top of
the ILD layer 67 and into the sides and bottom of holes 302, 303
and 304 are covered with a barrier (seed) layer 101. Subsequently,
a metal material 102 fills the holes 302, 303 and 304, on top of
the barrier layer 101 to form metal pillars 65, 68 and 70. The
metal pillars formed at this step are dispersed (or embedded) in
the ILD layer 67.
In an exemplary manufacturing process, Physical Vapor Deposition
(PVD) is used to deposit a barrier/seed layer 101 and Chemical
Vapor Deposition (CVD) is used for the metal material 102. The
barrier layer 101 is deposited on top of the ILD layer 67 and the
metal material 102 is deposited on top of the barrier/seed layer
101.
It should be noted that the use of PVD to layer the barrier/seed
layer 101 and the use of CVD to layer the metal materials 102 is
exemplary only and other methods, such as atomic layer deposition
(ALD), or electro-plating, are contemplated. The remaining metal
material 102, or the metal material that covers the ILD layer 67
but that is not in the holes 302, 303 and 304, is planarized using
chemical-mechanical polishing (CMP) until substantially only the
pillars 65, 68 and 70 remain embedded in the ILD layer 67. CMP is
used to remove excess metal material from metal layer 102 and the
barrier/seed layer 101 thereby advantageously preventing
short-circuits between pillars 65, 68 and 70 to undesirable
electrical components. Pillar 68 is used to pass current from the
source 60 to the MTJ 76. Pillar 70 serves to ground the MTJ 76.
In an exemplary embodiment, the metal material 102 is made of
tungsten. It should be noted that use of tungsten is exemplary only
and that the use of other conductive material that does not
chemically react with silicon is contemplated.
After the contact definition step 12 in FIG. 1 is performed, an ILD
step 14 is performed during which, an intermediate ILD layer 71 is
deposited on top of the ILD layer 67, covering substantially the
entire ILD layer 67, and pillars 65, 68, and 70. In an exemplary
application, Silicon Oxide (SiO.sub.2) is used as the ILD layer 71.
It should be noted that the use of SiO.sub.2 is exemplary only and
other forms of ILD layers are contemplated. Typically, a thinner
layer of SiN is deposited prior to the SiO.sub.2 layer to create an
etch stop for the subsequent etch process step 16.
After the ILD step 14 in FIG. 1, a metal area definition and
etching step 16 is performed during which a metal deposition area
104 is defined, which is an area substantially on top of the ILD
layer 67 and above pillars 68, 65 and 70. Subsequently,
photo-resist 75, which is shown in FIG. 5a, is applied to
substantially the entire top surface of the ILD layer 71 and
patterned. ILD layer 71 is etched until the pillars 68, 65 and 70
are exposed. In an exemplary application, RIE is used to etch the
ILD layer 71. It should be noted that the use of RIE to etch the
ILD layer is exemplary only and other forms of etching are also
contemplated.
After the metal area definition and etching step 16 in FIG. 1 is
completed, a metal barrier (seed) layer 101 is deposited on top of
the ILD layer 71 and into the sides and bottom of holes are covered
with a barrier (seed) layer 101. Subsequently, a metal material 106
fills the holes on top of the barrier layer 101 to form metal
pillars 72, 73 and 74, as shown in FIG. 2. The metal pillars formed
at this step are dispersed (or embedded) in the ILD layer 71. The
width of the metal pillars 72, 74 and 73 are each defined by the
metal deposition area 104. In an exemplary application, the metal
material 106 is copper. The use of copper is exemplary only and the
use of other metals is also contemplated. Steps 16 and 18 are
collectively a form of a Damascene process where trenches and vias
are formed and thereafter filled with metal, such as copper, in the
process flow of FIG. 1. While only a single metal is mentioned,
other metal layers may be formed on top of a previous metal layer,
separated by vias, in which case the MTJ 76 is formed in between
the second to the top and the top-most layer and the top-most metal
layer.
After the metal deposition step 18, in FIG. 1, a metal
planerization step 20 is performed during which the metal material
106 is partially removed using CMP, leaving in place metal pillars
72, 74 and 73 (collectively known as "intermediate metal pillars"),
and the ILD layer 71, as shown in FIG. 2. The metal pillar 72 is
advantageously low in resistance and substantially thin in size
thereby increasing power efficiency for the non-volatile magnetic
memory elements included in the memory cell. For example, the metal
pillar 72 may be made of copper, which has a very low resistance of
approximately 0.05 ohm/square and a thickness of 2000 to 4000
Angstroms. It should be noted that all resistance and thickness
values for the pillar 72 are exemplary only and other resistance
values and thicknesses are also contemplated.
It should be noted that pillars 65, 73, and 74 are not present in
every single memory cell. In an exemplary application, pillars 65,
70, 73, and 74 are formed every eighth circuit, but it is
contemplated this number might change. It is shown in FIG. 2 to
show how circuits with pillars 65, 70, 73, and 74 look. FIG. 2a
shows a circuit without pillars 65, 70, 73, and 74. In embodiments
where the pillars 65, 70, 73, and 74 are included only every so
many, such as eight, circuits, is to reduce cell size hence reduce
the cost as well as to decrease power and increase the reliability
of the manufactured memory cell 1.
Alternatively, rather than the steps 14 through 20, a non-damascene
process comprised of steps 314 through 320 shown in FIGS. 1 and
2b-2h may used. If this alternative method is used, after the
contact definition step 12 in FIG. 1, a metal deposition step 314
is performed where a metal layer 322 is deposited covering
substantially the entire ILD layer 67 including the pillars 68 and
70. In an exemplary application, the metal layer is made of
aluminum. It should be noted that the use of aluminum is exemplary
only and the use of other conductive material is also contemplated.
For instance, aluminum with a cap of a harder metal like Ti to act
as a mechanical stop to the subsequent CMP process step 320 may be
employed.
After the metal deposition step 314 in FIG. 1, a metal area
defining and etching step 315 is performed where a photo-resist
pillar 324 are applied substantially above metal pillar 68. The
metal layer is etched until metal pillars 354 and 355 remain.
After the metal area defining and etching step 315 FIG. 1, an ILD
deposition step 316 is performed during which an ILD layer 326 is
deposited covering substantially the entire wafer including metal
pillars 354 and 355. In an exemplary application, Silicon Oxide
(SiO.sub.2) is used as the ILD layer 326. It should be noted that
the use of SiO.sub.2 is exemplary only and other forms of ILD
layers are contemplated.
After the ILD deposition step 316 in FIG. 1, a photo-resist
deposition and etching step 317 is performed during which photo
resist 357 is deposited across the entire ILD layer 326 except in
the defined area 358, which is substantially above metal pillars
354 and 355. After the photo resist is applied, the ILD layer 326
is etching until metal pillars 354 and 355 are exposed.
After the photo-resist deposition and etching step 317 in FIG. 1, a
metal deposition step 318 is performed during which a metal layer
360 is deposited over the entire wafer, filling in holes 359 and
361. In an exemplary application, tungsten is used. It should be
noted that the use of tungsten is exemplary only and the use of
other materials is contemplated.
After a metal deposition step 318 in FIG. 1, an ILD planerization
step 320 is performed during which the metal layer 360 is
planerized until only metal pillars 362 and 363 remain embedded in
ILD layer 326. This planerization process leaves metal pillars 362
and 363 and ILD layer 326.
After the metal planerization step 20 or ILD planerization step 320
in FIG. 1, a conductive metal-cap deposition step 22 is performed
during which a conductive metal cap 108 is applied on top of the
ILD layer 71 and metal pillars 72, 73 and 74. The conductive metal
cap 108 allows for modular fabrication by sealing the non-volatile
magnetic memory cell. The conductive metal cap 108 advantageously
protects the pillars 72, 73 and 74 from oxidizing during transport
by manufacturing the memory in multiple stages. For example, during
the FEOL stage 15, the transistor 61 and non-magnetic portions of
the memory cell 1 are manufactured and during to a magnetic
fabrication stage 25, the magnetic material portion of the memory
cell 1 is manufactured. During fabrication, a number of stages of
manufacturing are performed. For example, in the embodiment related
to and method of FIG. 1, there are three stages of fabrication
shown. These stages include: FEOL 15, magnetic fabrication 25, and
BEOL 35 stages. The FEOL 15 facility is the facility used to
perform CMOS and/or non-magnetic metal fabrication. The BEOL 35
facility is the facility used to perform the subsequent metal
fabrication. By allowing for transport (modularity of the
processes), the need to have the FEOL 15, magnetic fabrication, and
BEOL 35 processes in the same facility is eliminated. This allows
for production in the least expensive CMOS factory without regard
to the BEOL 35 wherein the FEOL 15 further enhances
cost-effectiveness. Additionally, separating the FEOL 15 and the
BEOL 35 in separate facilities further prevents contamination of
the CMOS fabrication by the magnetic fabrication.
During magnetic fabrication 25 all the magnetic elements, namely
the MTJ 74, are deposited and formed. In the present application,
steps 10-22, and alternatively 314-320, comprise the FEOL 15. Steps
24-34 are included in the magnetic fabrication 25. Steps 36-46 are
included in the BEOL 35. It should be noted that the use of FEOL
15, magnetic fabrication 25, and BEOL 35 are exemplary only.
Further, it is contemplated that two or more of these stages may be
combined into a single stage in the same fabrication facility.
The conductive metal cap 108 also provides a smoother surface for
the MTJ 76 to be positioned thereon. A lower surface roughness
allows for advantageously forming the MTJ, which results in a
higher tunneling-magneto resistance (TMR). An exemplary average
surface roughness (Ra) of the metal cap 108 is 10 angstroms or
smoother. The metal cap 108 helps to control the surface roughness
onto which the MTJ 76 is deposited. The conductive metal cap 108
also advantageously increases the height of the MTJ 76. This
improves the CMP error threshold because less attention need be
given to avoid over-planarization, which is a known problem with
CMP methods. This leads to faster CMP thereby decreasing
manufacturing time. That is, the conductive metal cap 108
advantageously raises the height of the MTJ 76 that is to be
positioned thereon. This increases the CMP error threshold thereby
increasing the reliability of manufacturing. Increased reliability
in manufacturing allows for a better reliability (i.e. a higher
percentage of working memory cells-per-wafer), thereby reducing the
cost-per-element. The increase in speed also decreases fabrication
time, increasing yield, thereby further decreasing overall
cost.
In one embodiment of the present invention, the metal cap 108 is
typically less than 500 Angstroms in its thickness. When compared
with the thickness of metal pillar 72, the metal cap 108 is
anywhere typically less than 1/4th as thick.
In an exemplary application the conductive metal cap 108 is made of
tantalum nitride (TaN), and has a resistivity of approximately 20
micro Ohms-centimeter. It should be noted that all resistance and
thickness values for the conductive metal cap 108 and any other
layer are merely exemplary and different resistance values and
thicknesses are contemplated. It also should be noted that the use
TaN as the cap layer is exemplary only and that other conductive
metal materials are contemplated. These other conductive metal
material are preferrably conductive and substantially non-reactive
so as to avoid oxidation, and have a high melting point (e.g.
greater than 1200 degrees Celcius), and have a resistivity less
than 100 micro Ohms-cm, and a deposited film Ra of less than 20
Angstroms. If the deposited film Ra is higher than 20 Angstroms,
but otherwise meets the criteria, it will be kiss-polished to less
than 20 Angstroms. "Kiss-polish" refers to a very short or light
polishing process without having much material removal (typically
less than 10 nm of the underlying material) than the preceding
polish. Examples of suitable materials include but are not limited
to Tantalum, Chromium, Molybdenum, Tungsten, Niobium, Titanium,
Zirconium, Vanadium and Ruthenium. In addition, the conductive
metal cap 108 may be formed from any alloy that substantially meets
the criteria. Also, mixtures containing less than 1% nitrides of a
suitable material are also contemplated.
It should also be noted that use of a single layer of metal
material metal cap 108 is exemplary only and it is contemplated
that layers of different crystalline and amorphous metal materials
may be formed together. In an exemplary application of a layered
approach, copper nitride (CuN) and tantalum (Ta) may be layered
together to reduce resistance and/or decrease the average roughness
(Ra). However, other combinations of crystalline and amorphous
materials may be used.
After the conductive metal-cap deposition step 22 in FIG. 1, a
magnetic tunnel junction film (MTJ) deposition step 24 is performed
during which the MTJ film 110 is layered on top of the conductive
metal cap 108. The MTJ film 110 is layered onto the conductive
metal cap 108 using a cluster tool. A cluster tool is a tool for
applying varying materials without breaking vacuum. It is necessary
here because of the various ways a MTJ can be formed. The following
applications provide further details of various MTJs that can be
used to comprise the memory cell 1, the disclosures of which are
herein incorporated by reference as though set forth in full: U.S.
application Ser. No. 11/674,124, filed Feb. 12, 2007, titled
"Non-Uniform Switching Based Non-Volatile Magnetic Based Memory" by
Ranjan et alia, U.S. application Ser. No. 11/678,515, Filed Feb.
23, 2007, titled "A high capacity low cost multi-state magnetic
memory" by Ranjan et alia, U.S. application Ser. No. 11/739,648
Filed Apr. 24, 2007, titled "Non-volatile magnetic memory with low
switching current and high thermal stability" by Ranjan et alia,
U.S. application Ser. No. 11/776,692, filed Jul. 12, 2007, titled
"Non-Volatile Magnetic Memory Element with Graded Layer" by Ranjan
et alia, U.S. application Ser. No. 11/740,861, filed Mar. 26, 2007,
titled "High capacity low cost multi-stacked cross-line magnetic
memory" by Ranjan et alia, U.S. application Ser. No. 60/863,812,
filed Nov. 1, 2006, titled "Novel spintronic device" by Wang, U.S.
application Ser. No. 11/932,940 filed Oct. 31, 2007 titled
"current-confined effect of magnetic nano-current-channel (NCC) for
magnetic random access memory (MRAM)" by Wang, U.S. application
Ser. No. 11/866,830 filed Oct. 3, 2007, titled "Improved high
capacity low cost multi-state magnetic memory" by Ranjan et alia,
and U.S. application Ser. No. 11/860,467 filed Sep. 24, 2007,
titled "Low cost multi-state magnetic memory" by Ranjan et
alia.
MTJs other than those disclosed in the patent documents above are
contemplated. A conductive metal cap 112 is then formed on top of
the MTJ film 110. The conductive metal cap 112 essentially serves
as the top electrode of a memory element. In an exemplary
embodiment, the conductive metal cap 112 is made of Ta. In another
embodiment, the conductive metal cap 112 is approximately 40
nanometers in thickness.
After the MTJ deposition step 24 in FIG. 1, a photo resist step 26
is performed during which photo-resist pillars 114 are formed above
metal pillars 72, 73 and 74, as is later shown in FIG. 11.
After the photo resist step 26 in FIG. 1, an MTJ etching step 28 is
performed during which the conductive metal cap 112 and MTJ film
110 are partially etched leaving a pillar of conductive-metal
pillar 78 and MTJ (or MTJ pillar) 76, as shown in FIG. 2. In an
exemplary application, the MTJ etching step 28 is done in two
stages. The first stage is a selective etching used to target the
conductive metal cap 112. The second stage selectively etches the
MTJ film 110. In an exemplary application, the first stage is
accomplished using carbon tetrafluoride (CF4) and the second stage
is accomplished using methanol (CH3OH) or carbon monoxide
(CO)+ammonia (NH3) etching. It should be noted that the two-stage
etching and use of CF4, CH3OH and CO+NH3 are exemplary only and the
use of other gases are also contemplated. In addition, in an
exemplary application, after etching the top electrode is
approximately 20 to 60 nanometers thick.
After the MTJ etching step 28 in FIG. 1, a pillar passivation step
30 is performed during which the MTJ 76 and conductive metal pillar
78 are covered with a passivation layer 116 to protect the MTJ from
oxidization and other damage during potential transport from the
magnetic fabrication 25 to BEOL 35 facilities. In an exemplary
application, the passivation layer 116 is formed using silicon
nitride (Si3N4). Si3N4 is a dielectric material with excellent
protective qualities. The use of Si3N4 is exemplary only and other
materials that are non-conductive, have good adhesion, and a
temperature deposition of below approximately 350 degrees Celsius
are also contemplated. Other such materials include, but are not
limited to, silicon nitride (SiN), silicon oxy-nitride (SiON),
zirconium oxide (ZrO2), zirconium nitride (ZrN), hafnium oxide
(HfO2), and hafnium nitride (HfN).
After the pillar passivation step 30 in FIG. 1, a photo resist step
32 is performed during which photo resist is applied over the
passivation layer 116 as shown in FIG. 14. The photo resist area is
substantially larger than the MTJ 76 and conductive metal cap 78.
The larger size is to advantageously avoid redeposition during
etching. Redeposition is a process whereby material from one area
is moved to another during etching. Redeposition affects memory
cell 1 reliability and yield. In addition, a larger etching area
allows for greater variation in MTJ 74 placement. A larger
variation in MTJ placement reduces the number of non-functioning
memory cells by assuring an electrical connection and reduces the
number of quality assurance steps.
After the photo resist step 32 in FIG. 1, a MTJ etch step 34 is
performed during which the passivation layer 116 and conductive
metal cap 108 is etched away except in the over-sized area
substantially above the MTJ 76 and conductive metal pillar 78,
leaving conductive metal pillar 74, MTJ 76, conductive metal pillar
78, and passivation cap 80.
The passivation cap 80 is typically made of oxide and nitrides of
transition metals which are readily available for high volume
Integrated Circuit (IC) manufacturing. Examples of materials that
the passivation cap 80 is made of include, but are not limited to,
silicon nitride (Si3N4), silicon nitride (SiN), silicon oxy-nitride
(SiON), zirconium oxide (ZrO2), zirconium nitride (ZrN), hafnium
oxide (HfO2), hafnium nitride (HfN), tantalum nitride (TaN),
titanium nitride (TiN), tantalum oxide (Ta2O5), aluminum oxide
(Al2O3), or aluminum nitride (AlN). The passivation cap 80 is the
passivation layer 116 after the latter has been patterned.
After etching the MTJ is substantially oval in shape with a
Length/Depth ratio (L/D ratio) ranging from 1 to 3. This L/D ratio
is achieved during the etching process by selective application of
the photo-resist mask. Unlike other etching applications, there is
generally no use of optical pattern correction (OPC). OPC is
commonly used to maintain a substantially square edge during
etching. However, it is desirable to have an oval shape for the MTJ
to decrease switching current which may require some unique OPC
depending upon the resulting shape and size of the etched pillar as
well as the process conditions. In an exemplary application, RIE
with an etch rate of greater than 0.1 Angstroms/sec is used to etch
the passivation layer 116. Specifically, gases are used which have
a substantially gaseous by-product and the by-products are vacuumed
away during etching. RIE with gaseous by-products advantageously
reduces the number of steps by eliminating the need for a cleaning
step. In addition, RIE with a substantially gaseous by-product
produces less re-deposition, which advantageously increases
reliability, as discussed above. For example, carbon monoxide (CO)
may be used to etch the MTJ. It should be noted, however that the
use of RIE with gaseous by-products is exemplary only and other
forms of etching are contemplated. Other forms of RIE may be used
such as a chlorine etching. In addition, ion milling (also "ion
bombardment") may be used to etch the passivation layer 116.
However, ion milling causes significant redeposition and requires
additional clean-up steps.
After the MTJ etch step 34 in FIG. 1, an ILD deposition and
planerization step 36 is performed during which an ILD layer 118 is
deposited on ILD layer 71 and metal pillars 72, 74 and 73. In an
exemplary application, the ILD layer 118 is silicon oxide
(SiO.sub.2) but it should be noted that other materials are
contemplated
Referring now to FIGS. 2i-2l, showing the stages of the CMP process
in step 36 to include a plurality of stages. After the ILD layer
118 is deposited, ILD layer 118 is planerized using CMP until
substantially the top of the conductive metal pillar 78 is
exposed.
Referring now to FIG. 2i, showing a cross section of the wafer to
include ILD layer 71, metal pillar 72, conductive metal cap 74, MTJ
76, conductive metal cap 76, passivation layer 116, and ILD layer
118. FIG. 2i shows a small hump 130 over the MTJ 76.
Referring now to FIGS. 2i and 2j, the small hump 130 that forms
above the MTJ 76 as part of the deposition process is flattened
using CMP so that the ILD layer 118 is flat.
Referring now to FIG. 2k, the ILD layer 118 is planerized using CMP
until the top of the passivation cap 80 is exposed. Passivation cap
80 results from the patterning of the passivation layer 16.
Referring now to FIG. 2l, the CMP slurry is changed and the
passivation cap 80 is planerized using CMP until the top of
conductive metal pillar 78 is exposed.
After the ILD deposition and planerization step 36 in FIG. 1, a
metal deposition step 38 is performed during which a metal layer
120 is deposited on top of the ILD layer 118 and MTJ-stack top 77.
In an exemplary application, aluminum is used for this step. It
should be noted that other metals are also contemplated.
After the metal deposition step 38 in FIG. 1, a photo resist step
40 is performed during which photo resist 121 is patterned into
bars on top of the metal cap 120 as shown in FIG. 18.
After the photo resist step 40 in FIG. 1, a metal etching step 42
is performed during which the metal cap 120 is etched away leaving
metal bars 122. The metal bars connect multiple conductive metal
caps 78 in order to pass a current and read from and write to the
non-volatile magnetic memory cell. In an exemplary application, RIE
is used to etch the metal bars 122. It should be noted that the use
of RIE is exemplary only and other forms of etching are
contemplated.
After the metal etching step 42 in FIG. 1, a passivation step 44 is
performed during which a passivation layer 124 is deposited
encapsulating the metal bars 122. The passivation layer 124 is
necessary to prevent undesirable electrical connections between
electrical components.
After the passivation step 44 in FIG. 1, a contact pads step 46 is
performed during which contact pads are opened up to the memory
cell 1 allowing the memory cells to connect to the rest of the
circuits and logic.
FIGS. 3-21 show 3-dimensional views of the relevant part of a wafer
306 onto which memory cells are formed in accordance with the
method of FIG. 1. Each figure shows six memory cells.
Referring now to FIG. 3 which shows the structure of the memory
cell 1 after the CMOS step 10 has been completed, the source 60 and
drain 62 are shown to be formed substantially parallel to one
another. The gate 69 is shown to be form substantially on top of
the source 60, drain 62, and the channel 64 is formed substantially
underneath the gate.
FIGS. 3a and 3b show the structure of memory cell 1 after the
contact definition step 12. In FIG. 3a, the photo-resist 58 is
shown to be patterned on top of the ILD layer 67 except in the
contact area 100, as noted above. In FIG. 3b, the barrier layer 101
is shown to fill the hole 302. The barrier layer 101 is formed on
top of the ILD layer 67 as well as in the hole 302.
FIG. 4 shows the structure of the memory cell 1 after the step 12.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67 and metal contact pillar 68. The
metal contact pillar 68 is shown formed substantially on top of the
source 60. The ILD layer 67 is shown formed substantially around
the metal pillar 68 and of substantially the same thickness as the
metal pillar 68.
FIGS. 5 and 5a show the structure of the memory cell 1 after the
step 14. In FIG. 5, the memory cell 1 is shown to include the drain
62, source 60, channel 64, gate 69, ILD layer 67, metal contact
pillar 68, and ILD layer 71. The ILD layer 71 is shown formed
substantially over the ILD layer 67 and metal contact pillar 68. In
FIG. 5a, the memory cell 1 is shown when photo-resist 75 is applied
on top of the ILD layer 71.
FIG. 6 shows the structure of the memory cell 1 after the step 16.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, and a
post-etch ILD layer with pillar holes 73. The post-etch ILD layer
with pillar holes 73 is shown formed above the ILD layer 67 and
metal contact pillar 68.
FIG. 7 shows the structure of the memory cell 1 after the step 18.
The memory cell 1 is shown to the drain 62, source 60, channel 64,
gate 69, ILD layer 67, metal contact pillar 68, post-etch ILD layer
with pillar holes 73, and metal material 106. The metal material is
formed above the post-etch ILD layer with pillar hole 73. The metal
material is also formed in such a way as to fill the pillar holes
in the post-etch ILD layer will pillar holes.
FIG. 8 shows the structure of the memory cell 1 after the step 20.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, and metal pillar 72. The metal pillar 72 is shown to be
formed substantially above metal contact pillar 68 so as to make
electrical contact. ILD layer 71 is shown formed around metal
pillar 72 and formed of substantially the same thickness as metal
pillar 72.
FIG. 9 shows the structure of the memory cell 1 after the step 22.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, and conductive metal cap 108. The
conductive metal cap 108 is shown formed substantially above the
ILD layer 71 and metal pillar 72.
FIG. 10 shows the structure of the memory cell 1 after the step 24.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ film 110,
and conductive metal cap 112. The MTJ film is shown formed
substantially on top of the conductive metal cap 108. The
conductive metal cap 112 is shown formed substantially on top of
the MTJ film 110.
FIG. 11 shows the structure of the memory cell 1 after the step 26.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ film 110,
conductive metal cap 112 and photo-resist pillars 114. The
photo-resist pillars are shown formed on top of the conductive
metal cap 112 and are positioned substantially in line with the
metal pillar 72 along the vertical axis
FIG. 12 shows the structure of the memory cell 1 after the step 26.
The memory cell 1 is shown to include drain 62, source 60, and
resistor 64, ILD layer 67, metal contact pillar 68, ILD layer 71,
metal pillar 72, conductive metal cap 108, MTJ 76, and conductive
metal pillar 78. While in FIG. 12, the MTJ 76 and conductive metal
pillars are shown as square in shape, other shapes, including but
not limited to, circles and ovals are also contemplated. Non-square
shapes prove advantageous because they decrease the current
required to operate the non-volatile magnetic memory cell.
FIG. 13 shows the structure of the memory cell 1 after the step 28.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, and passivation layer 116. The cap area
is raised in the area substantially above the conductive metal
pillar 78.
FIG. 14 shows the structure of the memory cell 1 after the step 32.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, Si3N4 layer 116, and photo resist
pillars 117. The photo resist is formed substantially above the MTJ
76 and conductive metal pillar 78.
FIG. 15 shows the structure of the memory cell 1 after the step 34.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, and passivation cap 80. The passivation
cap 80 substantially encapsulates the conductive metal cap 74, MTJ
76, and conductive metal pillar 78.
FIG. 16 shows the structure of the memory cell 1 after the step 36.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, passivation cap 80, and ILD layer 118.
The ILD layer 118 is then planerized using CMP to expose the
MTJ-stack top 77.
FIG. 17 shows the structure of the memory cell 1 after the step 38.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, passivation cap 80, ILD layer 118, and
the metal cap 120. The metal cap is formed substantially on top of
the ILD layer 118.
FIG. 18 shows the structure of the memory cell 1 after the step 40.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, passivation cap 80, ILD layer 118, a
metal cap 120, and a photo resist bars 121. The photo resist bars
are formed on top of the metal cap 120 and substantially above the
conductive metal caps 78.
FIG. 19 shows the structure of the memory cell 1 after the step 42.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, passivation cap 80, ILD layer 118, and
metal bars 122. The metal bars are formed substantially above the
conductive metal pillar 78 and connect multiple memory cells in
order to pass current and operate them.
FIG. 20 shows the structure of the memory cell 1 after the step 44.
The memory cell 1 is shown to include the drain 62, source 60,
channel 64, gate 69, ILD layer 67, metal contact pillar 68, ILD
layer 71, metal pillar 72, conductive metal cap 108, MTJ 76,
conductive metal pillar 78, passivation cap 80, ILD layer 118,
metal bars 122, and a passivation layer 124. The passivation layer
is formed substantially on top of the metal bars 122 and ILD layer
118.
FIG. 21 shows the structure of the memory cell 398 after step 314.
The memory cell 398 is shown to include the drain 62, source, 62,
resistor 64, ILD layer 67, metal contact pillar 68, and metal layer
322. In an exemplary embodiment the metal layer 322 is made out of
copper. It should be noted that this is exemplary only and other
materials are contemplated.
FIG. 22 shows the structure of the memory cell 398 after step 316.
The memory cell 398 is shown to include the drain 62, source, 62,
resistor 64, ILD layer 67, metal contact pillar 68, and metal
pillars 72.
FIG. 23 shows the structure of the memory cell 398 after steps 318
and 320. The memory cell 398 is shown to include the drain 62,
source, 62, resistor 64, ILD layer 67, metal contact pillar 68, ILD
layer 71 and metal pillars 72. Although the present invention has
been described in terms of specific embodiments, it is anticipated
that alterations and modifications thereof will no doubt become
apparent to those skilled in the art. It is therefore intended that
the following claims be interpreted as covering all such
alterations and modification as fall within the true spirit and
scope of the invention.
* * * * *